A supported metal catalyst for thermal oxidative degradation of polyester plastics and a preparation method and application thereof

Abstract

The application belongs to the field of catalysts, and particularly relates to a supported metal catalyst for thermal oxygen degradation of polyester plastics and a preparation method and application thereof. The supported metal catalyst is prepared according to the following steps: a) under stirring, a silica-alumina molecular sieve is immersed in an aqueous solution of a metal salt; after the immersion is completed, a solid-phase product is collected by centrifugation to obtain a catalyst precursor; in step a), the silica-alumina molecular sieve is one or more of ZSM molecular sieves, USY molecular sieves, LSP molecular sieves and TS-1 molecular sieves; the metal salt is one or more of nickel salt, copper salt, cobalt salt and iron salt; the temperature of the immersion is 20-100 DEG C; b) the catalyst precursor is calcined under aerobic conditions to obtain the supported metal catalyst. The preparation process of the supported metal catalyst is simple, the cost is low, and the supported metal catalyst has high activity, selectivity and stability in a solvent-free thermal oxygen degradation reaction of polyester plastics.

Description

Technical Field

[0001] The invention belongs to the field of catalysts, and in particular relates to a supported metal catalyst for thermal oxidation degradation of polyester plastics, a preparation method and an application thereof. Background Art

[0002] With the rapid development of human society, white pollution caused by discarded plastics has become a major problem in global environmental governance. On the other hand, plastic waste is one of the underdeveloped carbon resources. Therefore, recycling and reusing the large amount of existing plastic waste can not only alleviate future environmental pressures, but also optimize the energy structure and realize the transition from fossil energy to renewable energy. Polyethylene terephthalate (PET) is the fourth largest source of plastic waste. However, due to factors such as low monomer recovery rate, difficulty in purification, expensive catalysts, and secondary pollution of solvents, PET and most other wastes are currently recycled through mechanical technologies such as crushing, extrusion, and recycling.

[0003] By catalytically degrading plastic waste and converting it into high-value chemicals such as monomers and fuels, it can not only effectively reduce the negative impact of plastics on the environment, but also promote the recycling of carbon resources. Thermal catalysis is a common method for the value-added of plastic waste, without the need for additional separation or pretreatment of mixed polymer waste, but the conversion process requires harsh reaction conditions, high energy consumption and safety risks. At present, the adjustable acidity and unique pore structure in molecular sieve catalysts can improve the selectivity of plastic degradation products. Loading metal on molecular sieves can further enhance the activity of the degradation reaction and further increase the degradation rate. In order to achieve sustainable development under the background of the dual carbon strategy, it is urgent to design and develop efficient, low-cost, thermally stable and highly active catalysts to realize the resource utilization of waste plastics. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a supported metal catalyst for the thermal oxidation degradation of polyester plastics, and its preparation method and application. The supported metal catalyst provided by the present invention has a simple preparation process, low cost, and has high activity, selectivity and stability.

[0005] The present invention provides a method for preparing a supported metal catalyst for thermal oxidative degradation of polyester plastics, comprising the following steps:

[0006] a) impregnating the silicon-aluminum molecular sieve in a metal salt aqueous solution under stirring; after the impregnation is completed, collecting the solid phase product by centrifugation to obtain a catalyst precursor;

[0007] In step a), the silicon-alumina molecular sieve is one or more of ZSM molecular sieve, USY molecular sieve, LSP molecular sieve and TS-1 molecular sieve; the metal salt is one or more of nickel salt, copper salt, cobalt salt and iron salt; the impregnation temperature is 20-100° C.;

[0008] b) calcining the catalyst precursor under oxygen conditions to obtain a supported metal catalyst.

[0009] Preferably, in step a), the concentration of the metal salt in the metal salt aqueous solution is 0.006-0.1 mol / L; and the usage ratio of the metal salt aqueous solution to the silica-alumina molecular sieve is 50 mL: (0.5-1.5) g.

[0010] Preferably, in step a), the immersion time is 3 to 10 hours.

[0011] Preferably, in step a), the stirring speed is 400-1000 rpm.

[0012] Preferably, in step a), the centrifugal speed is 6000-12000 rpm, and the time is 2-10 min.

[0013] Preferably, in step a), the collected solid phase product is washed and dried.

[0014] Preferably, in step b), the calcination temperature is 300-800° C. and the calcination time is 2-6 hours.

[0015] The present invention provides a supported metal catalyst for thermal oxidation degradation of polyester plastics, which is prepared according to the preparation method described in the above technical solution.

[0016] The present invention provides a method for thermal oxidation catalytic degradation of polyester plastics, comprising the following steps:

[0017] In the presence of the supported metal catalyst described in the above technical solution and under oxygen conditions, the polyester plastic is heated and degraded to obtain a degradation product.

[0018] Preferably, the temperature of the heating degradation is 210-300° C., and the time is 1-100 h.

[0019] Compared to the prior art, the present invention provides a supported metal catalyst for the thermal oxidation degradation of polyester plastics, as well as its preparation method and application. The supported metal catalyst provided by the present invention is prepared according to the following steps: a) impregnating a silica-alumina molecular sieve in a metal salt aqueous solution under stirring; after the impregnation, centrifuging and collecting the solid phase product to obtain a catalyst precursor; in step a), the silica-alumina molecular sieve is one or more of ZSM molecular sieve, USY molecular sieve, LSP molecular sieve, and TS-1 molecular sieve; the metal salt is one or more of nickel salt, copper salt, cobalt salt, and iron salt; the impregnation temperature is 20-100°C; b) the catalyst precursor is calcined under aerobic conditions to obtain the supported metal catalyst. The supported metal catalyst provided by the present invention has simple preparation steps, mild preparation conditions, and low preparation cost; during the preparation process, the catalyst uses electrostatic adsorption and ion exchange methods to uniformly disperse the metal in the form of nanoparticles or single atoms on the silica-alumina molecular sieve carrier, achieving highly dispersed active sites and significantly improving the reaction activity of the catalyst; moreover, because the catalyst has a special and stable coordination environment, as well as the synergistic effect between the activity of the supported non-precious metal and the acidity of the molecular sieve carrier, it has the advantages of high reaction activity, good selectivity, and strong stability in the selective catalytic oxidation degradation reaction of plastics. In short, the supported metal catalyst provided by the present invention not only has a simple preparation method and low preparation cost, but also has excellent catalytic performance and high product selectivity when used as a catalyst for the oxidation degradation reaction of polyester plastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0021] Figure 1 X-ray diffraction patterns of the catalysts of Examples 1 and 2 provided by the present invention;

[0022] Figure 2 Transmission electron microscope images of the catalysts of Examples 1 and 2 provided by the present invention;

[0023] Figure 3 This is a graph showing the yield of the target product, terephthalic acid, when the catalyst of Example 1 provided by the present invention is reused. DETAILED DESCRIPTION

[0024] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0025] The present invention provides a method for preparing a supported metal catalyst for thermal oxidative degradation of polyester plastics, comprising the following steps:

[0026] a) impregnating the silicon-aluminum molecular sieve in a metal salt aqueous solution under stirring; after the impregnation is completed, collecting the solid phase product by centrifugation to obtain a catalyst precursor;

[0027] b) calcining the catalyst precursor under oxygen conditions to obtain a supported metal catalyst for thermal oxidation degradation of polyester plastics.

[0028] In the preparation method provided by the present invention, in step a), the silicon aluminum molecular sieve is one or more of ZSM molecular sieve, USY molecular sieve, LSP molecular sieve and TS-1 molecular sieve, wherein the ZSM molecular sieve is preferably H-type ZSM-5 molecular sieve, more preferably NH4 + The H-type ZSM-5 molecular sieve after exchange; the silicon-aluminum ratio of the silicon-aluminum molecular sieve is preferably 30-200, specifically 60-75 or 130-150.

[0029] In the preparation method provided by the present invention, in step a), the metal salt is one or more of nickel salts, copper salts, cobalt salts and iron salts; the anion of the metal salt is preferably nitrate; the concentration of the metal salt in the metal salt aqueous solution is preferably 0.006-0.1 mol / L, specifically 0.006 mol / L, 0.008 mol / L, 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L or 0.1 mol / L.

[0030] In the preparation method provided by the application, in step a), the ratio of the use amount of the aqueous metal salt solution to the silicon-aluminum molecular sieve is 50 mL:(0.5-1.5) g, and specifically, it can be 50 mL:0.5 g, 50 mL:0.55 g, 50 mL:0.6 g, 50 mL:0.65 g, 50 mL:0.7 g, 50 mL:0.75 g, 50 mL:0.8 g, 50 mL:0.85 g, 50 mL:0.9 g, 50 mL:0.95 g, 50 mL:1 g, 50 mL:1.05 g, 50 mL:1.1 g, 50 mL:1.15 g, 50 mL:1.2 g, 50 mL:1.25 g, 50 mL:1.3 g, 50 mL:1.35 g, 50 mL:1.4 g, 50 mL:1.45 g or 50 mL:1.5 g.

[0031] In the preparation method provided by the application, in step a), the temperature of the impregnation is 20-100℃, and specifically, it can be 20℃, 30℃, 40℃, 50℃, 60℃, 70℃ or 80℃; and the time of the impregnation is preferably 3-10 h, and specifically, it can be 3 h, 4 h, 5 h, 6 h or 7 h. In the application, the metal monatomic (M SA ) loaded silicon-aluminum molecular sieve catalyst can be obtained at an impregnation temperature of 60℃; and the metal particle (M NP ) loaded silicon-aluminum molecular sieve catalyst can be obtained at an impregnation temperature of 80℃. In the application, the impregnation reaction temperature and time affect the metal loading form and coordination environment, and further affect the plastic thermal oxidation catalytic degradation activity of the catalyst product.

[0032] In the preparation method provided by the application, in step a), the stirring speed is preferably 400-1000 rpm, and specifically, it can be 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, 800 rpm, 850 rpm, 900 rpm, 950 rpm or 1000 rpm. In the application, the stirring treatment can improve the divergence and stability of the metal, and further affect the plastic thermal oxidation catalytic degradation activity of the catalyst product.

[0033] In the preparation method provided by the present invention, in step a), the centrifugal speed is preferably 6000-12000 rpm, specifically 6000 rpm, 6500 rpm, 7000 rpm, 7500 rpm, 8000 rpm, 8500 rpm, 9000 rpm, 9500 rpm, 10000 rpm, 10500 rpm, 11000 rpm, 11500 rpm or 12000 rpm; the centrifugal time is preferably 2-10 min, specifically 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min, 9.5 min or 10 min. In the present invention, the centrifugal step affects the divergence and loading of the metal, thereby affecting the plastic thermal oxidative degradation activity of the catalyst product.

[0034] In the preparation method provided by the present invention, in step a), the collected solid phase product is preferably washed and dried. The purpose of the washing is to remove excess ions on the solid phase product; the washing method is preferably water washing and / or alcohol washing; the drying method is preferably oven drying; the drying temperature is preferably 60 to 80°C, specifically 60°C, 65°C, 70°C, 75°C, or 80°C; and the drying time is preferably 5 to 20 hours, specifically 5 hours, 10 hours, 15 hours, or 20 hours.

[0035] In the preparation method provided by the present invention, in step b), the aerobic condition is preferably a pure oxygen atmosphere or an air atmosphere.

[0036] In the preparation method provided by the present invention, in step b), the calcination temperature is preferably 300-800°C, more preferably 350-600°C, and specifically 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C or 600°C; the calcination time is preferably 2-6 hours, and specifically 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours. In the present invention, the calcination heat treatment affects the type and amount of oxygen species in the catalyst, thereby affecting the thermal oxidation catalytic activity of the catalyst.

[0037] The present invention also provides a supported metal catalyst for the thermal oxidative degradation of polyester plastics, which is prepared according to the preparation method described in the above technical solution. In the present invention, the metal loading of the supported metal catalyst is preferably 0.02 to 2 wt% as calculated using inductively coupled plasma testing, and specifically can be 0.02 wt%, 0.05 wt%, 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 1.7 wt%, or 2 wt%.

[0038] The present invention also provides a method for thermal oxidation catalytic degradation of polyester plastics, comprising the following steps:

[0039] In the presence of the supported metal catalyst described in the above technical solution and under oxygen conditions, the polyester plastic is heated and degraded to obtain a degradation product.

[0040] In the method for thermal oxidation catalytic degradation of polyester plastics provided by the present invention, the polyester plastics include but are not limited to polyethylene terephthalate; the polyester plastics are preferably in the form of fragments or powders.

[0041] In the method for thermal oxidation catalytic degradation of polyester plastics provided by the present invention, the aerobic condition is preferably a pure oxygen atmosphere or an air atmosphere.

[0042] In the method for thermal oxidation catalytic degradation of polyester plastics provided by the present invention, the temperature of the heating degradation is preferably 210-300°C, specifically 210°C, 215°C, 220°C, 225°C, 230°C, 235°C, 240°C, 245°C, 250°C, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, 285°C, 290°C, 295°C or 300°C; the time of the heating degradation is preferably 1-100h, specifically 1h, 5h, 10h, 20h, 50h, 70h or 100h.

[0043] The loaded metal catalyst provided by the technical solution of the present invention is mainly through electrostatic adsorption and supplemented by ion exchange, so that the non-precious metal iron is evenly dispersed in the form of single atoms on the silica-alumina molecular sieve carrier, which is not easy to aggregate into particles in large quantities and has high reaction activity. Due to the special and stable coordination environment and the synergistic effect between the loaded non-precious metal single atoms and the silica-alumina molecular sieve acid sites, the catalyst has the advantages of high activity, good selectivity, and strong stability. In the oxidative degradation reaction of polyester plastics, the silica-alumina molecular sieve loaded metal catalyst provided by the technical solution of the present invention has excellent catalytic performance. In short, the loaded metal catalyst provided by the technical solution of the present invention not only has high activity, high selectivity and high stability, but also has a simple preparation method and low preparation cost, and can show excellent catalytic performance in the oxidative degradation reaction of polyester plastics.

[0044] For the purpose of greater clarity, the present invention is described in detail with reference to the following examples.

[0045] Example 1

[0046] A ZSM-5 molecular sieve supported iron catalyst is prepared by the following steps:

[0047] 50mL of 0.06M Fe(NO)3·xH2O and 1g of NH4 with a silicon-aluminum ratio of 130-150 + The exchanged H-type ZSM-5 was mixed uniformly, stirred and impregnated at 60°C and 600 rpm for 6 hours, then cooled to room temperature, and then centrifuged at 10,000 rpm for 5 minutes. The obtained product was then washed with deionized water to remove nitrate ions, then washed with alcohol, and dried at 80°C to obtain a catalyst precursor.

[0048] The catalyst precursor obtained by drying was placed in a muffle furnace and calcined at 550 ° C for 3 h in an air atmosphere, and then cooled to room temperature to obtain a silicon-aluminum molecular sieve catalyst mainly loaded with iron single atoms, named Fe SA / ZSM.

[0049] Specifically, during the implementation of Example 1 of the present invention, the following test results were obtained:

[0050] (1) X-ray diffraction was used to analyze the Fe SA / ZSM was characterized, and the results are shown in Figure 1 .Depend on Figure 1 The results show that the Fe SA There is no obvious diffraction peak of iron species in the / ZSM catalyst, which proves that it is a single iron atom.

[0051] (2) The Fe SA / ZSM observation, the results are shown in the upper left and upper right figures of Figure 2, Figure 2 The upper left picture is a transmission electron microscope image of FeSA / ZSM, and the upper right picture is a distribution diagram of iron elements in the transmission electron microscope test of FeSA / ZSM. Figure 2 The results show that the Fe SA / ZSM catalyst has single iron atoms uniformly dispersed on the ZSM-5 support.

[0052] (3) The Fe SA / ZSM catalyst was used as a catalyst for the oxidative degradation reaction of PET plastic and its performance was tested. The specific process is as follows:

[0053] During the PET oxidation degradation process, 50 mg of PET powder (50 μm, M w : 20000~200000), 30 mg of the catalyst prepared in Example 1 of the present invention is added to the reactor, and pure oxygen at normal pressure is introduced by means of air bags, balloons or gas cylinders. Set the reaction temperature and time, and cool to room temperature after the reaction is completed. The reactor should have a condensation part so that the sublimated solid product terephthalic acid can be fully condensed. After the reaction is completed, open the reactor and use a polar organic solvent such as dimethyl sulfoxide to dissolve the solid product terephthalic acid, and filter and separate it. The separated solid catalyst is washed and dried for reuse. The separated terephthalic acid product is analyzed by a nuclear magnetic resonance spectrometer to obtain the following: Figure 3 The product performance diagram shown in FIG. Figure 3 It can be seen that the catalyst prepared in Example 1 of the present invention has strong performance in oxidative degradation of polyester plastics. At a reaction temperature of 260°C and pure oxygen conditions, the catalyst can withstand oxidation and produce terephthalic acid with a selectivity of greater than 99% with high activity, and there is no obvious attenuation after 6 cycles using polyethylene terephthalate as the reaction substrate.

[0054] Example 2

[0055] The preparation process of the catalyst is the same as that of Example 1, except that the temperature during the impregnation of the metal salt solution and the silica-alumina molecular sieve is changed to 80°C. A silica-alumina molecular sieve catalyst mainly loaded with iron nanoparticles is obtained, which is named Fe NP / ZSM.

[0056] During the implementation of Example 2 of the present invention, the following test results were obtained:

[0057] (1) X-ray diffraction was used to analyze the Fe NP / ZSM was characterized, and the results are shown in Figure 1 .Depend on Figure 1 The results show that the Fe NP / ZSM catalyst has no obvious iron species metal diffraction peak.

[0058] (2) The Fe NP / ZSM observation, the results are shown in the lower left and lower right figures of Figure 2, Figure 2 The lower left picture shows Fe NP Transmission electron microscope image of / ZSM, the lower right image is Fe NP / ZSM transmission electron microscope test of iron distribution. Figure 2 The results show that the Fe NP The ZSM / ZSM catalyst consists of iron nanoparticles dispersed on a ZSM-5 support.

[0059] (3) The Fe NP The ZSM catalyst was used as a catalyst for the oxidative degradation reaction of PET plastic and its performance was tested. The specific process was the same as in Example 1. The results showed that the oxidative depolymerization reaction of the plastic had high activity and selectivity greater than 99%.

[0060] Example 3

[0061] The catalyst preparation process is the same as that in Example 1, except that 50 mL of 0.03 M Fe(NO)3·xH2O and 1 g of NH4 with a Si / Al ratio of 130-150 are used. + The exchanged H-type ZSM-5 is mixed evenly.

[0062] The reaction performance test was the same as that in Example 1, and the plastic oxidative depolymerization reaction had high activity and selectivity greater than 99%.

[0063] Example 4

[0064] The catalyst preparation process is the same as that in Example 1, except that 40 mL of 0.06 M Fe(NO)3·xH2O and 1 g of NH4 with a Si / Al ratio of 130-150 are used. + The exchanged H-type ZSM-5 is mixed evenly.

[0065] The reaction performance test was the same as that in Example 1, and the plastic oxidative depolymerization reaction had high activity and selectivity greater than 99%.

[0066] Example 5

[0067] The preparation process of the catalyst is the same as that of Example 1, except that copper nitrate and ferric nitrate are used alone or together as metal sources and loaded on the silica-alumina molecular sieve.

[0068] The reaction performance test was the same as that in Example 1, and the plastic oxidative depolymerization reaction had high activity and selectivity greater than 99%.

[0069] Example 6

[0070] The preparation process of the catalyst is the same as that of Example 1, except that a layered pillared zeolite (LSP) type molecular sieve is used.

[0071] The reaction performance test was the same as that in Example 1, and the plastic oxidative depolymerization reaction had high activity and selectivity greater than 99%.

[0072] Example 7

[0073] The preparation process of the catalyst is the same as that of Example 1, except that a silica-alumina molecular sieve with a silica-alumina ratio of 60-75 is used.

[0074] The reaction performance test was the same as that in Example 1, and the plastic oxidative depolymerization reaction had high activity and selectivity greater than 99%.

[0075] Example 8

[0076] The catalyst preparation process is the same as that in Example 1, except that 1 L of 0.06 M Fe(NO)3·xH2O and 20 g of NH4 with a Si / Al ratio of 130-150 are used. + The exchanged H-type ZSM-5 is mixed evenly.

[0077] The reaction performance test was the same as that in Example 1, and the plastic oxidative depolymerization reaction had high activity and selectivity greater than 99%.

[0078] Example 9

[0079] The preparation process of the catalyst was the same as that of Example 1, except that the stirring impregnation reaction was performed at 70°C.

[0080] The reaction performance test was the same as that in Example 1, and the plastic oxidative depolymerization reaction had high activity and selectivity greater than 99%.

[0081] Example 10

[0082] The preparation process of the catalyst was the same as that of Example 1, except that the stirring impregnation reaction time was 5 h.

[0083] The reaction performance test was the same as that in Example 1, and the plastic oxidative depolymerization reaction had high activity and selectivity greater than 99%.

[0084] Example 11

[0085] The catalyst preparation process was the same as in Example 1, except that the impregnation reaction was stirred at a speed of 800 rpm.

[0086] The reaction performance test was the same as that in Example 1, and the plastic oxidative depolymerization reaction had high activity and selectivity greater than 99%.

[0087] Example 12

[0088] The preparation process of the catalyst was the same as that of Example 1, except that the centrifugal speed was 8000 rpm and the time was 7 min.

[0089] The reaction performance test was the same as that in Example 1, and the plastic oxidative depolymerization reaction had high activity and selectivity greater than 99%.

[0090] Example 13

[0091] The preparation process of the catalyst was the same as that of Example 1, except that the drying temperature was set to 70° C. after stirring and centrifuging.

[0092] The reaction performance test was the same as that in Example 1, and the plastic oxidative depolymerization reaction had high activity and selectivity greater than 99%.

[0093] Example 14

[0094] The preparation process of the catalyst was the same as that of Example 1, except that oxygen atmosphere was used as the calcination oxidizing atmosphere.

[0095] The reaction performance test was the same as that in Example 1, and the plastic oxidative depolymerization reaction had high activity and selectivity greater than 99%.

[0096] Example 15

[0097] The preparation process of the catalyst was the same as that of Example 1, except that the calcination temperature was 450° C. and the calcination time was 4 h.

[0098] The reaction performance test was the same as that in Example 1, and the plastic oxidative depolymerization reaction had high activity and selectivity greater than 99%.

[0099] Example 16

[0100] The preparation process and performance test method of the catalyst were the same as those in Example 1, except that the reaction substrate polyethylene terephthalate (PET) was replaced by polybutylene adipate (100 μm, M w :30000~200000). According to the test, the plastic oxidative depolymerization reaction has high activity and selectivity greater than 99%.

[0101] Example 17

[0102] The catalyst preparation process and performance testing methods were the same as in Example 1, except that atmospheric pressure air was introduced during the thermal oxidative degradation of polyethylene terephthalate. Testing showed that the plastic oxidative depolymerization reaction had high activity and selectivity greater than 99%.

[0103] In summary, the embodiments of the present invention not only have high activity, high selectivity and high stability, but also have a simple preparation method and low preparation cost, and can exhibit excellent catalytic performance in the oxidative degradation reaction of polyester plastics.

[0104] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for thermal oxidation catalytic degradation of polyester plastics, characterized in that: The following steps are involved: In the presence of a supported metal catalyst and oxygen conditions, polyester plastic is thermally degraded to obtain degradation products; The supported metal catalyst is prepared according to the following steps: a) impregnating the silicon-aluminum molecular sieve in a metal salt aqueous solution under stirring; after the impregnation is completed, collecting the solid phase product by centrifugation to obtain a catalyst precursor; In step a), the silicon-alumina molecular sieve is one or more of ZSM molecular sieve, USY molecular sieve, LSP molecular sieve and TS-1 molecular sieve; the metal salt is one or more of nickel salt, copper salt, cobalt salt and iron salt; the impregnation temperature is 20-100°C; b) The catalyst precursor is calcined under oxygen conditions to obtain a supported metal catalyst for thermal oxidative degradation of polyester plastics.

2. The method for thermal oxidation catalytic degradation of polyester plastics according to claim 1, characterized in that: In step a), the concentration of the metal salt in the metal salt aqueous solution is 0.006-0.1 mol / L; and the usage ratio of the metal salt aqueous solution to the silica-alumina molecular sieve is 50 mL: (0.5-1.5) g.

3. The method for thermal oxidation catalytic degradation of polyester plastics according to claim 1, characterized in that: In step a), the immersion time is 3 to 10 hours.

4. The method for thermal oxidation catalytic degradation of polyester plastics according to claim 1, characterized in that: In step a), the stirring speed is 400-1000 rpm.

5. The method for thermal oxidation catalytic degradation of polyester plastics according to claim 1, characterized in that: In step a), the centrifugal speed is 6000-12000 rpm, and the time is 2-10 min.

6. The method for thermal oxidation catalytic degradation of polyester plastics according to claim 1, characterized in that: In step a), the collected solid phase product is washed and dried.

7. The method for thermal oxidation catalytic degradation of polyester plastics according to claim 1, characterized in that: In step b), the calcination temperature is 300-800° C. and the calcination time is 2-6 hours.

8. The method for thermal oxidation catalytic degradation of polyester plastics according to claim 1, characterized in that: The heating degradation temperature is 210-300° C., and the time is 1-100 hours.

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